Milo g



. M. G. KELLOGG. MULTIPLE SWITGHBOARD.

Patented Oct. 26,1897.

z a, wk

llk nlu u Eill U I w W k I (No Model.)

NITED STATES PATENT WFFICE.

MILO G. KELLOGG, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE KELLOGG SVITCI-IBOARD AND SUPPLY COMPANY, OF SAME PLACE.

MULTIPLE SWITCHBOARD.

SPECIFICATION forming part of Letters Patent No. 592,350, dated October 26, 1897.

Application filed January 2, 1890. Serial No. 335,700. (No model.)

To all whom, it may concern.-

Be it known that I, MILO G. KELLOGG, of Chicago, in the county of Cook and State of Illinois, temporarily residing at Stuttgart, in the Empire of Germany, have invented certain new and useful Improvements in Multiple Switchboards for Telephone-Exchanges, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to a telephone-exchange system in which the lines are singlecircuit lines grounded at their outer ends; and it consists of apparatus for switching such lines of the exchange, in the operation of the exchange system, and a system of testing the lines to determine whether they are in use.

In the drawings illustrating my invention, Figures 1 and 1" represent sections of two multiple switchboards of the exchange to which the same lines are connected. Fig. 2 shows a diagram of the boards with the main line apparatus and connections necessary to illustrate my invention. Fig. 2 is a detail view of one of the line-annunciators. Fig 3 shows a diagram of an operators cord system to be used in connection with the boards. Fig. 4. shows an operators test system to be used at the boards. Fig. 5 shows a subscribers-station apparatus.

G in each case represents a ground connection.

In Fig. 2,A is a sectional view of the switchboard shown in Fig. 1, and A is asectional view of the switchboard shown in Fig. 1, each as indicated by the line cl 6.

I place as many boards in the central office as are found necessary or desirable in order to properly operate the exchange. On each board is a spring-jack or other suitable switch for each line. Each switch has a contactspring which normally connects with an insulated contact-piece and is adapted to receive a loop-plug and, when a plug is inserted, to disconnect the spring from the contactpiece and connect the two contact-pieces of the plug with the spring and said insulated contact-piece,respectively. The switch is also adapted to receive a single-contact switchplug and, when a plug is inserted, to disconmeet the spring from the contact-piece and connect the spring with the contact-piece of the plug. In the construction of the switches, as shown and as will hereinafter be described, I prefer to have a contact-point electrically connected with the contactpiece and on which the spring normally bears, as there is less chance of poor connection when the spring bears on a point than when it bears on asurface adapted to be brought into connection with the plug-contacts.

In Fig. 2, g g represent the springs of the different switches, h h the contact-points on which the springs normally bear and the contact-pieces of the switches connected with the points 7t h. Z Z are the switch-holes. a Z) are the rubber strips on which the metal parts of the switches are mounted, as shown, and through the fronts of which are the switch holes 1 Z.

The contact-piecesjj are so placed along one of the surfaces of the plug-holes as readily to form connection with one of the contactpieces of the loop-plugs.

The holes H are adapted to receive the switch-plugs shown in Fig. 3 and marked D D, and when a plug is inserted into a switch it raises the spring 9 from the contact-point h, and the spring 9 and contact-piece of the plug are in contact. These holes are also adapted to receive the loop-plug shown in Fig. 4, and when a plug is inserted into a hole it raises the spring of the switch from the contact-point 72,, and the spring 9 and the contactpiece j of the switch are in contact with the two contact-pieces of the plug, respectively.

to and 56 are calling-annunciators, one for each of the lines shown. Each annunciator has a pair of contact-points normally (or when the annunciator does not indicate a call) in contact with each other, but which are separated by the annunciator while it indicates a call. The two contact-points of a pair are marked 19 and g, respectively. One of them,q, is a spring-contact which is pressed by the annunciator-drop when the drop falls away from its corresponding contact-point p. The contact-point p is represented as an angle-piece which passes over the spring q and is in contact with the spring when the spring is not actuated by the annunciator-drop.

the subscribers stations any usual and appro- E priate subscribers-station apparatus. Each line passes successively through the pairs of contacts of its switches on the several boards, passing to each spring first. It then passes through its line-annunciator and the pair of annunciator contact-points to the ground. The circuit of each line shown may thus be traced in Fig. 2.

In the operators cord system shown in Fig. 3, D D are the switch-plugs of a pair of cords.

n n are the rubber insulations of the plugs, Q

and m m are their contact-pieces. These contact-pieces pass each to the bottom of its plug and are adapted to rest normally or when the plugis not in use on the metal piece 0, which then connects it with the ground. Weights, as is usual, or similar devices may be used to bring the contact-pieces of the plugs into contact with the piece 0 and secure a good connection.- These plugs are adapted to be inserted into any of the switches at their hoard,and when a plug is inserted it operates the switch, as above described. The plugs should be inserted so that the contact-piece m is in contact with the spring g. The connections of the lines might have been reversed, so that the lines pass first to the contact-piecej of each of their switches, and in that case the plugs should be inserted in such a position that their contact-pieces form connection with the pieces j of their switches. Y is thelooping-in switch for the pair of cords shown. is is the calling-key, and o is a clearing-out annunciator. tis the operators telephone, and B is her calling generator or battery. The circuits are substatantially as shown.

The two levers of the looping-in switch are connected by means of flexible conductors to the two contact-pieces of the switch-plugs.

' The contact-bolts of one of the pair of the erator or battery.

The operation of the system in connection with the switch-boards will be apparent to those skilled in the art. 7

i It will readily be apparent that when a linejs switched by the insertion of a plug into its switchthe line is disconnected from its normal ground at the central offi cc and is connected into a circuit with the pair of cords. Only one pair of cords isshown, but the connection of such other pairs, with their accompanying apparatus, as the operator may need 1 will be apparent to those skilled in the art.

To each pair of cords, with its plugs, belong a looping-in switch, a clearing-out annunciator, and a calling-key. One telephone and one calling-generator will answer for her system of cords.

In the operators test system shown in Fig. 4, T is a loop test-plug adapted to be inserted into any of the switches, and when inserted to operate them, as heretofore described.

; B is a test-battery, and S is a test receiving instrument. The battery and instrument are connected in a loop which terminates in the two contact-pieces of the plug.

Each operator has one cord system and one test syste1n,and they are conveniently mounted and arranged for her work.

In the subscribers-station apparatus shown in Fig. 5, 1 is the telephone-switch. 2 is the calling-generator. 3 is the signal-receiving hell. 4 is the subscribers telephone. 5is the secondary, and 6 is the primary, of the induction-coil. 7 is the transmitter. 8 is the transmitter-battery, and 9 is a condenser. These parts may be of usual forms of appa ,ratus and are connected as shown or in other ways so as to perform practically the operations required andthe operations hereinafter described.

When the subscribers telephone is on its IIO ary and primary of the induction-coil to the lever of the switch, and thence through the signal-bell and calling-generator to ground. A circuit-wire of small resistance passes from the line between the subscribers station and the condenser to a contact point, against which the switch-lever is in contact when the telephone is on the lever. Another wire of small resistance passes from the circuit between the signal-bell and the office ground to a contact-point against which the lever comes in contact when freed from the weight of the telephone. A third circuit-wire passes from the connection between the primary and secondary of the induction-coil, through the transmitter and battery, to a contact-point against which the switch lever comes in contact when relieved of the weight of the telephone.

through an annunoiator tact-points normally closi the annunciator indicates tion with pairs of switch-p the two contact-pieces of e nected by a flexible-cord c plugs being adapted to be switch at its board and W1 connect the pair of conta normally in contact and c( point which is connected the contact-piece of the plt a switch at the subscriber tact-points to switch the l circuit of the line While switched for use and out o of the line when the teleph loop test-plugs, one at eac plug having two contact-I min'ate the two sides of a1 a test receivinginstrume being adapted to be insert switches at its board an disconnect the contact-pt and connect them with th the plug, and battery in tablished on testing, eaci strulnent and battery being justed that the instrument are included in the norm: any line but will not soun is open at any point or th with another line or the phone is switched for use is thereby included in th tially as set forth.

7. In a telephone-excha: ple switchboards, telepho grounded at its outer end lines, one switch for each I each switch having a pail normally in contact, but or switched at their board, 921A t *al i at L th I a ed tnhe is "lit ich )ny, bed in- ;he ,ctits lat led nd y inc for in any 

